Written by Prof Carl Amos, with pictures contributed by several MSC ECE students;
MSc students from the Engineering in the Coastal Environment Course joined with final year undergraduates in Oceanography for a field trip to Highcliffe and Hengistbury. The trip shows the impact of coastal protection works at Highcliffe that is creating significant erosion of 4-5 m/year) downdrift (to the east) due to terminal groyne syndrome. The engineering works of Highcliffe include short and long rock groynes, drainage culverts, cliff toe stabilization, and beach recharge with gravel. There is still a longshore and cross-shore movement of gravel at about 2000 cubic metres/year.
Hengistbury Head is the peninsula that separates Christchurch Bay from Poole Bay (to the west). Much of the material entering the sedimentary cell of Christchurch passes eastwards around Hengistbury Head. The construction of the Long Groyne in 1938 has significantly reduced the volume of material moving eastwards resulting in breaching and erosion of Mudeford Spit. The coastal stability from Bournemouth to Barton on Sea was presented and discussed, and the remedial measures that have taken place to protect the region from erosion and flooding.
Most significant was the recent rock-falls (see photo) of the western cliffs of Hengistbury Head that resulted from the 28 October storm that created a surge of around 1 m. This region is vulnerable to further erosion unless protected and could lead to a breach into Chrischurch Harbour through the Double Dykes region unless future protection is provided.